which resin for thick pour PERFECT finish?

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#1

Hello. my first post.

I am trying to find an appropriate resin to use, i need to make up to a 1" thick pour over a sandwich core fiberglass flat.

Cure time or working time isnt an issue, i would prefer less than 2 hours set time. indoor/ outdoor not important. color not important.

  1. ) the top surface needs to be consistent, meaning no swelling or shrinking during the curing process. i will be leveling out the flat and pouring the resin on top, and then polishing after.

  2. ) i need to be able to polish it perfectly. i need a surface finish as close as possible to glass, looking thru a magnifying glass. no material texture if possible.

I have seen UV resin, and 1:1 tabletop resin, but i have no experience with these. i have used hardware store epoxy and poly resin for years with fiberglass parts, some parts Vacuum bagged.

Cost is somewhat an issue, i would prefer a cheaper product for final prototype and then for the next one i am willing to pay more for it. By this i mean i would like a +/- 80% choice with these characteristics, and then a more expensive solution that works 100% with these terms.

thanks in advance for your help!

#2

Look for the bar top epoxy. It’s the stuff you see on the bar tops and can be poured very thick. The cure time is extra slow so there is no discoloration or over exotherming. I think you can even get a polyester resin that is for this purpose… i’ve used it for jewelry. It’s not super cheap stuff but, epoxy generally isn’t cheap. You might also be able to find a polyurethane for this purpose.

What are you trying to do exactly? Cause another option is to put a piece of acrylic over it, has a similar effect.

#3

I polished out completely a sample of hardware store resin (polyester), the surface is acceptable so i guess any resin will work for my surface.

my major problem now is shrinking/ swelling. which type of resin will not shrink/ swell and will get hard? i know this is a newbie question, but i havent been able to determine which material will satisfy both. i am unsure if the casting resin gets hard, and i think this is the resin everyone says will not shrink/ swell?

more technical question- does it affect the distribution (shrinking/ swelling) if it is a 1:1 mix -vs- drops per oz?

(this project is a bit of a science experiment so i know it seems like off-the-wall questions. this is not something associated with structural design. sorry)

if i am asking too much of a resin then feel free to say so, and maybe other recommendations you have. air dry material will not work. UV cure seems like it will work perfect but i do not know if it shrinks/ swells or if it gets hard like poly resin.

(regarding acrylic sheet- surface shows too many waves. not perfectly flat. Lapping my flat piece would work, but would take an extensive amount of polishing. would prefer not to do this)

#4

Perfect finishes are always fun…

polyester is going to be a high shrink resin by nature. Though the slower you cure it the less shrinkage or discoloration you’ll have. For thick pouring the resins I"ve seen usually have a long cure time of like a few days. This type of resin is cosmetic.

About your question for a mix… you’re talking polyester? If so, then you’re adding catalyst, MEK-p. Then you want to add by weight, though we’ve all probably just done it by volume. And you’re going to add a small percentage, like 1-3% depending on temperature and working time.

If it’s epoxy, you must follow the ratio given by the manufacturer. Measure by weight, and don’t alter the ratio. You usually have a 3% margin of error or so with epoxy.

So it sounds like you’re having some issues with the stuff you’ve tried? It’s always a science experiment right? WHich UV cure did you try? Haven’t had a chance to use that stuff, but hear it’s pretty good.

#5

i ordered the UV resin last week, poured it saturday. the hardness and consistency is good but the surface wasnt nearly as glossy as i had hoped, had texture on it. had to sand smooth and polish. still not done polishing. cured in a few mins as advertised. good clear color but has greenish-blue tint. color doesnt matter to me but in case anyone was curious.

still not near a glassy-watery flat surface so i guess the search continues.

it did shrink a lot, but im thinking the heat caused it because one area was overheated from thick pour. seems like this stuff likes to stay thin, about 1/8" max for best results over large surface.

so i guess i need a very slow curing epoxy. i was really hoping for a set time less than 2-3 hours. im not sure my setup will last a few days active. looks like tabletop epoxy might have to be the one. it will be a few weeks till i try it. im using an elec pump on a portion of the project and the cure time of the resin determines how long the motor has to run. might need to make a cooling system if this is my only option.

what are the properties of casting resin? (in terms of this discussion)
prototype #2 down. now on to #3.